Blood pressure (BP) measurement by a provider in the clinic, ?attended clinic BP?, is the primary method for diagnosing and managing hypertension (HTN). BP may differ inside versus outside of clinic. Ambulatory BP monitoring (ABPM) measures out-of-clinic BP. Compared with attended clinic BP, BP during the awake period on ABPM (?awake BP?) is a better predictor of cardiovascular (CVD) risk. Guidelines recommend ABPM to identify white coat HTN (having high clinic BP but not having high awake BP) and masked HTN (not having high clinic BP but having high awake BP). In most ABPM studies, white coat HTN is not associated with an increased risk of target organ damage and CVD, whereas masked HTN is associated with a two times increased risk of target organ damage and CVD. African Americans have a high prevalence of white coat and masked HTN. A question has arisen: is there a better approach to measure clinic BP without the need to conduct ABPM. One approach is to use an automated oscillometric device to measure clinic BP without a provider present (?unattended clinic BP?). In prior studies, compared to attended clinic BP, unattended clinic BP has been closer to awake BP, suggesting that unattended clinic BP may reduce the likelihood of white coat HTN. However, these studies had several methodological limitations: the order of clinic BP measurements was not randomized; attended and unattended clinic BP were not measured in the same individuals; attended clinic BP measurement was not performed according to guidelines; and samples were small, did not include African Americans, and only included those with high clinic BP. Scarce data also exist on whether unattended clinic BP reduces the likelihood of masked HTN. The goal of the study is to determine whether unattended versus attended clinic BP is closer to awake BP on ABPM, and whether unattended versus attended BP reduces the likelihood of white coat and masked HTN. We will enroll 2,775 adults from the fourth exam of the Jackson Heart Study (JHS), an African American cohort. Unattended and attended clinic BP measurement will be performed in random order using the same oscillometric device with attended BP performed according to guidelines; 24-hour ABPM will be conducted. Left ventricular hypertrophy (LVH) and chronic kidney disease (CKD) will be assessed. In Primary Aim 1, we will compare the mean absolute within-individual difference between clinic BP and awake BP on ABPM when clinic BP is measured unattended versus attended. In Primary Aim 2, we will compare the group prevalence of white coat HTN and masked HTN when clinic BP is measured unattended versus attended. In Primary Aim 3, we will determine whether masked HTN, defined using unattended clinic BP, is associated with LVH and CKD. This study will provide high quality empiric evidence which may impact future HTN guidelines. If unattended versus attended clinic BP is closer to awake BP on ABPM, and the likelihood of both white coat and masked HTN are reduced, then unattended BP should be the primary method of clinic BP measurement and ABPM may no longer be necessary.